Some of the corners you're asked to locate don't physically exist. The design calls for a point where two faces meet, but out on the site there's nothing to put a prism on — the corner spalled off, got rounded, is buried, is blocked by another element, or was never a solid corner in the first place. You still have to report where it is.
A point in space, not a thing you can touch
This comes up more than people expect. Two walls that stop short of each other, so the "corner" is a theoretical intersection hanging in the air. A footing corner that's broken away. A design point defined by the drawings but obstructed by rebar, formwork, or an adjacent pour. A weathered masonry corner that's rounded off to the point that there's no single spot that honestly represents it.
The instinct is to get as close as you can and call it — set the prism on the nearest solid thing and note it as the corner. But "close to where the corner should be" isn't the corner, and once that soft point leaves your hands it becomes the number everyone downstream builds to.
You don't need the corner — you need the two lines
The way out is to stop hunting for a point that isn't there and locate the two lines that define it instead.
Each face usually has a good, solid run somewhere away from the damaged or missing corner. Capture that run as a line. Do the same for the second face. Then extend both lines and cross them — the intersection is the corner, whether or not anything physical exists at that spot. You've reconstructed a point in space from two lines you could measure cleanly, instead of guessing at one you couldn't.
How the Precision Offset does it
The Precision Offset (PLO) is built around exactly this move. A fixed 3″ perpendicular offset off each face lets you define both lines from their good sections — two stored points per face — and the intersection of those lines gives you the corner at any angle, present or not. The missing corner stops being a problem because you never needed to occupy it.
It's the same principle as reading an odd-angle corner; here it just happens that the corner isn't physically there. Two clean lines beat one guessed point every time.
The takeaway from the dirt
A corner that isn't there is still a corner someone is going to build to. Guess at it and you've written a soft number into the design. Locate the two lines from the solid material you do have, cross them, and you hand off a real intersection — even when there was nothing standing at that spot to measure.
The Precision Offset takes a fixed 3″ perpendicular offset off any flat face — store two points to define a line, cross two lines for an intersection at any angle. 6061-T6 aluminum, stainless hardware, standard 5/8-11 mini-prism mount, made in the USA. See the specs →